The basic idea of the paper derives from the fact that the different activities of man is one of the most frequent sources of false alarms. After the definition of the problem, today's counter-measures are described, i.e. the various attempts to improve the false alarm situation by developing proper standards and codes and designing better hard- and software. The authors introduce an automatic fire detection system in which the fire sensitivity is controlled by so-called "presence detectors. This means in particular that depending on the presence or absence of man the fire detection sensitivity is automatically adapted. First experimental results of this new concept are reported.